Note: This information has been incorporated into this page which contains a more in-depth discussion.

I received an urgent phone call yesterday from a man who had digitized several reels of 2″ 24-track analog recordings that he wished to re-mix.

The tapes were originally recorded in about 1978-1979 and he said that he needed them to have Dolby C noise-reduction processing applied to the files.

I did a bit of research, as that did not sound correct from an historic point of view.

Here is an approximate chronology of the major noise-reduction systems and their dates of introduction: (more…)

We are currently working on some un-published tapes for a major Canadian folk artist. We have a 7.5 in/s 2-track stereo recording that was one of (if not the) first studio recording of this artist from circa 1972.

At some point, this tape was played on a 1/4-track machine that injected hum onto the left channel. Here’s what the magnetic viewer showed:

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I recently received two 7-inch reels of Kodak Type 31A Triacetate tape (1250 feet, Durol Base) that smelled of vinegar even before I got the envelope open.

These tapes were badly warped due, most likely, to the vinegar-syndrome induced differential shrinkage. Other factors may have been poor winding during long-term storage (I had received them after several attempts to play them on another machine). (more…)

We have pulled the list of degrading analog audio tapes out of the blog postings (which age) and put this information into the Formats hierarchy under Analog Audio Tapes, click here. Please note that we have fudged the hierarchy by starting the title with a hyphen, so it sorts to the top of the Analog Audio Tape grouping, above 0.15″ cassettes.

We hope to update this as we come across more types. January 2009 was, sadly, fruitful in finding at least some batch(es) of two tapes from 1990 (Agfa PEM 526) and 2003 (Emtec SM911) are degrading. The Emtec SM911 was thought to be more-or-less immune from this disease. As of this writing, it has been confirmed that batch number B0134007 was involved.

We have just seen a modification on the Sticky Shed Syndrome (SSS) failure mode. This is a case where the back-coat of the tape is turning to powder. The oxide was brown but yet it left a black, non-sticky accumulation of powder on the reproduce head. This accumulation would drastically reduce the high frequency response of the system due to spacing loss. We did bake the tape and we’re not sure that helped significantly, although it did not appear to make the problem worse. We would NOT recommend baking these tapes in the future. Ultimately, Pellon wiping of the mag coat during transfer after several pre-wipes for the length of the tape solved this.

Agfa PEM-526 exhibited this odd behaviour. The tape was recorded in 1990.

There is also a discussion about PEM-469 showing similar behaviour here.

For a current list of degrading analog tapes, click here.

I spent days trying to get Shamrock 031 to play without much success. Since this is an Ampex factory budget brand (probably non-spec premium tape) I thought that it might be suffering from Sticky Shed Syndrome. I baked it for 12 hours and it still squealed. I then tried my usually successful cold playing technique and it still squealed. Cold playing has worked successfully with 3M 175 and Sony PR-150.

I was getting rather frustrated and since it was a four-track tape and one of the techniques that is supposed to reduce squeal is to play the tape faster, I dragged out my Racal Store 4DS instrumentation recorder which has a 75,000 Hz bandwidth at 15 in/s and played it at 15 in/s and digitized it at 88,200 samples per second. After slowing it down 4x and ending up with a 10 kHz bandwidth (which I subsequently truncated to 5 kHz since there was no useful information above that, but lots of noise–same as the non-squealing portion of the real-time transfers on a Studer A810).

 

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A few months ago, I transferred several Tonschreiber tapes which were IG Farben Magnetophonband Typ C manufactured in Germany prior to the end of 1943. These had been stored in their almost-sealed steel cans and stunk. The best description of the smell was old lemon chicken.

We know that the sealed can will accelerate the vinegar syndrome degradation. The big question is are these tapes an anomaly or the mine canary for some (or all) acetate tapes?

The composite photo below shows some of the conditions that we found. Note especially the rolled outer strands showing extreme shrinkage from vinegar syndrome.

Click for a larger image.

We were able to transfer these tapes,  but the sound quality suffered due to the unsteadiness of the tape transport. The quality of the sound was due mostly to the fact that this was recorded at 30 in/s (probably 77 cm/s) with a full-track head. Nothing beats areal density for robustness.

A client phoned me and said a cassette he was playing started to shed in his machine and he stopped and took it out. He sent it to me and as I pulled a little bit of clear leader out of the middle of the tape, this is what I found:

Notice how the complete strips of oxide exist on their own, independent of the clear “leader” to which they previously were attached. (more…)

I received a cassette from a client and he complained that the previous recording was audible as well as the new recording.

There are several ways this can happen:

• The erase head can be dirty—this usually leads to high frequencies being erased and lower frequencies still audible
• The erase head can be misaligned—this often provides a partial erasure, but careful use of track selection can find a section of track with less crosstalk.
• A similar problem occurred on quarter-track reels with misaligned record heads where recordings from the opposite direction would invade the tracks for the forward directions. Again, a specially adjustable narrow head usually solves this.
• A completely non-functioning erase system—this is what we suspect happened with the current project. There were no track dissimilarities nor any other way we could find, including looking at the tape with the 8-track cassette recorder to separate the underlying, unwanted recording from the wanted one.
• A totally unrelated mechanism that may sound the same is if the microphone or tape recorder picks up a broadcast or other radiated signal and records that along with the desired signal.

We opted not to proceed with any noise gating as it would not improve the overall audio quality for listening and may actually impede transcrption.

While not a success, we were able to confirm to the client that there was no way that could preserve the fidelity of the desired sound and remove the undesired sound. The desired interview was completely intelligible and could be transcribed. It was just distracting to listen to.